1. Field of the Invention
The present invention relates to a novel carbazole derivative and a chemically amplified radiation-sensitive resin composition comprising the carbazole derivative suitable as a chemically-amplified resist useful for microfabrication utilizing various types of radiation represented by deep ultraviolet rays such as a KrF excimer laser, ArF excimer laser, EUV, or F2 excimer laser, X-rays such as synchrotron radiation, or charged particle rays such as electron beams.
2. Description of the Background Art
In the field of microfabrication represented by fabrication of integrated circuit devices, lithographic technology enabling microfabrication with a line width of 0.20 μm or less is demanded in recent years in order to achieve a higher degree of integration.
A conventional lithographic process utilizes near ultraviolet rays such as an i-line radiation. It is known in the art that microfabrication with a line width of a sub-quarter micron order using near ultraviolet rays is very difficult.
Therefore, use of radiation with a shorter wavelength has been studied for enabling microfabrication with a line width of 0.20 μm or less. As radiation with a shorter wavelength, deep ultraviolet rays represented by a line spectrum of a mercury lamp and an excimer laser, X-rays, electron beams, and the like can be given. Of these, a KrF excimer laser (wavelength: 248 nm), an ArF excimer laser (wavelength: 193 nm), and an F2 excimer laser (wavelength: 157 nm) have attracted attention.
As a resist applicable to the shorter wavelength radiations, a number of resists utilizing a chemical amplification effect between a component having an acid-dissociable functional group and a photoacid generator which generates an acid upon irradiation (hereinafter called “exposure”) has been proposed. Such a resist is hereinafter called a chemically amplified resist.
As a chemically amplified resist, Japanese Patent Publication No. 27660/1990 discloses a composition comprising a polymer having a t-butyl ester group of a carboxylic acid or t-butylcarbonate group of phenol and a photoacid generator. This composition utilizes the effect of the polymer to release a t-butyl ester group or t-butyl carbonate group by the action of an acid generated upon exposure to form an acidic functional group such as a carboxylic group or a phenolic hydroxyl group, which renders an exposed area on a resist film readily soluble in an alkaline developer.
In recent years, in addition to high limit resolution and high process margin, a high sensitivity to radiations is demanded of chemically amplified resists as a factor determining productivity of a photolithographic process.
Reducing the amount of basic substance which is a component of chemically amplified resists is one of the methods of increasing the sensitivity of the chemically amplified resists. This method, however, not only involves a decrease in the amount of acids produced by a photoacid generator, which gives rise to unduly roughened pattern surfaces, but also impairs environmental resistance of the resist such as poor PED stability, which is an indication of line width stability against a fluctuated period of time from exposure to post heat treatment. One method for obviating this problem is to increase the amount of photoacid generator. However, an increased amount of photoacid generator decreases radiation transmissivity through resist films, resulting in a trapezoid pattern profile rather than a desirable rectangular pattern profile.
In an effort of increasing sensitivity by the use of additives, Japanese Patent Application Laid-open No. 34272/2000 discloses a method of adding a cyclic 1,2-diolmonosulfonate compound as an agent to assist acid generation. However, this method may affect storage stability of radiation-sensitive resin compositions. When the photoacid generator is accidentally decomposed for some reason, an acid may be rapidly produced due to the action of the acid generation assisting agent.
The effect of carbazole compounds to increase the sensitivity of succinimide esters used as a photoacid generator has been reported (J. Am. Chem. Soc. 1988, 110, 8736). However, this type of compound is highly toxic and readily sublimable. The compound may splash when forming resist patterns, soils the exposure apparatus, and may have an adverse effect on human bodies.
Accordingly, development of a non-sublimable resist additive capable of increasing sensitivity without affecting basic photo-resist performance such as high resolution and pattern profile, and providing a chemically amplified radiation-sensitive resin composition possessing high environmental resistance and storage stability is strongly desired.
Therefore, an object of the present invention is to provide a novel carbazole derivative which is very useful as a component for increasing sensitivity of a chemically amplified resist having sensitivity to radiation such as deep ultraviolet rays represented by a KrF excimer laser, ArF excimer laser, and F2 excimer laser, and a radiation-sensitive resin composition comprising such a carbazole derivative exhibiting superior sensitivity as a resist without affecting basic resist performance such as resolution, pattern profile, and stability to resist fluctuations of the period of time from exposure to post heat treatment, and suitably used as a chemically amplified resist possessing excellent environmental resistance and storage stability.